In a gas turbine, because high-temperature working fluid flows in the area surrounding turbine blades, in general, cooling channels are formed inside the turbine blades in the longitudinal direction of the turbine blades, and cooling of the turbine blades is performed by streaming cooling air through the cooling channels. Part of the air compressed by a turbine compressor is extracted and fed into the cooling channels as the cooling air, and this cooling air flows through the cooling channels to cool the turbine blades from inside, thereby protecting the turbine blades from the heat of the high-temperature working fluid (combustion gas). Known conventional gas turbines (gas turbine blades) employing such a configuration include technology disclosed in Patent Literature 1.
In the conventional gas turbine disclosed in Patent Literature 1, a single-space hollow portion is formed from a base side of a turbine blade toward a tip side thereof, whereas a plurality of straight-channel-like elongated holes are formed from the tip side of the turbine blade toward the base side thereof; and these elongated holes communicate with the hollow portion at a mid portion of the turbine blade in the longitudinal direction. In addition, the hollow portion is widened at the portion communicating with the elongated holes. Accordingly, when forming the elongated holes from the tip side of the turbine blade by machining, the elongated holes are readily made to communicate with the hollow portion, and machining thereof is easy.